I took out the cups on an old bike I was working on (a 1989 specialized stumpjumper comp). The spindle was shot but the cups are good. When I threaded the fixed cup, I noticed that it was tight on one side and not flush on the other. The gap is right around 1.5 mm. I don't believe that the BB shell is cross threaded as the threads look fine on the fixed cup and it threaded in easily enough (I needed a tool to turn it in parts as the fitting is a little tight but this did not require any force). It certainly is tight for the last few turns but there is paint in the shell so I'm not surprised. I'm guessing that this is the way the BB shell came straight from the factory.

I know cup and cone takes a fair amount of misalignment but is 1.5 mm something to be concerned about? I'd rather not pay to have the BB shell faced. This is just a commuter bike but one I really like so I'd consider getting some work done on it. It bugs me that the cup is that far out on one side, however. Should I get the shell faced and the threads chased?

bikemig, If it's not due to paint on the BB faces, I think you should if you're going to repair the BB. Internal cartridge BBs are more forgiving of non parallel BB shell faces than non cartridge internal BBs or external BBs.

Brad

1.5mm is a lot of shell face "offness". It's possible, but i question if the shell is OK and the cup was crossed instead. If the shell was not well faced the cup would cock a bit on tightening and the wear path inside would show it's misalignment too. Does the wear path look concentric and even of is it off too? It's pretty easy to cross thread a cup, fine thread pitch for the diameter and often cups or shells have quite partial thread heights.

Now chasing and facing a shell is almost always a good thing to do and this procedure would show if the shell was really off. Buy I would be surprised if the shell was that far off. One can take a machinist's square and lay the body against the shell's face and see how the blade runs WRT the shell's OD. Doing this at a few points around the face will show quickly any major face/shell non squareness. (In fact this is how I faced the first few frames i built back in the late 1970s). If the shell face was off by 1.5mm across it's diameter the square's blade will be close to 3mm off along the shell's side at it's other face. That's a lot and VERY to see.

Do this before you spend $ for a facing job and let us know what is found. Andy.

Andy: this is great stuff; thanks (and to bradtx as well). I'm suspicious of the 1.5 gap as well which is why I posted this. I've never seen a gap that big. I thought that the dang thing must be cross threaded but the cup turns pretty easily and the threads don't look bad. It is tight in spots, though, which is not a good sign (and very, very tight at the very end just before the cup touches the shell). I thought that when a cup was cross threaded that it would be very difficult to turn but that is not the case here.

I don't have a machinist's square, though. I should be able to use a carpenters square, right? Now I just have to go out and buy one which will make the wife happy as she'll no doubt find a project for me to use it on,

Edit: my camera is only so-so but I'll see if I can post some decent pics of the cup tonight. I tried to thread a different cup and it felt tight and I immediately backed off (no reason to ruin another cup) which suggests that cross threading is the real problem.